Acadia's remlifanserin narrowly misses primary endpoint in Phase 2 Alzheimer's psychosis study

Acadia Pharmaceuticals announced on September 24, 2026 topline results from the Phase 2 portion of its RADIANT trial program testing remlifanserin in patients with Alzheimer's disease psychosis (ADP), which the company described as Phase 3 enabling.

On the primary endpoint, change from baseline in the Scale for the Assessment of Positive Symptoms-Hallucinations and Delusions subscales, once daily 60 mg remlifanserin demonstrated a change of -12.6 versus a -10.4 change for placebo at week 6, yielding a standardized effect size of 0.26, with a p-value of 0.0603.¹ That fell short of statistical significance.

On the key secondary endpoint, Clinical Global Impression - Severity, the 60 mg dose showed a change from baseline of -1.3 compared with -0.9 for placebo at week 6, for a standardized effect size of 0.37, reaching nominal significance at p=0.0077.¹ The gap between the 60 mg dose and placebo widened over the six-week treatment period on both measures.¹

By contrast, the lower 30 mg dose produced only minimal improvement across endpoints versus placebo.¹ The analyses were conducted in a pre-specified modified full analysis set population.¹

On safety, rates of adverse events, serious adverse events and discontinuations were similar to placebo across both doses, there was no signal of QT prolongation, the data suggested no negative effect on motor symptoms or cognition, and no deaths occurred in the remlifanserin arms.¹

Based on these findings, Acadia intends to keep enrolling its two ongoing Phase 3 ADP studies while amending the Phase 3 program, including dropping the 30 mg dose arm.¹ Detailed results are scheduled for an oral presentation at the Clinical Trials on Alzheimer's Disease conference, running November 16-19, 2026 in Boston.¹ Remlifanserin is also being studied separately in a Phase 2 trial for Lewy body dementia psychosis.¹